Put your led blinking code (the code lines that check millis() and switch the led on/off) into a new function. Call this function after each individual piece of data is sent to the GSM modem, as well as somewhere at the top or bottom of loop().
Put your led blinking code (the code lines that check millis() and switch the led on/off) into a new function. Call this function after each individual piece of data is sent to the GSM modem, as well as somewhere at the top or bottom of loop().